Abstract: The Mw 5.5 Pohang earthquake occurred on 15 November 2017 close to two 4 km-deep boreholes drilled as part of South Korea’s first enhanced geothemal system (EGS) project and within 5 km of the city of Pohang. The experimental EGS project was intended to demonstrate the feasibilty of geothermal energy production in southeastern South Korea as the country develops low-carbon energy technologies. The earthquake caused dozens of hospitalizations, one fatality, the displacement of 1700 people into emergency housing, and total economic impact of ~US$300M. It’s location close to the EGS site led to immediate concern that EGS activities had played some role in the earthquake’s nucleation. The key finding of the government inquiry into the earthquake’s causes was that high-pressure injection of water into one of the two boreholes had unequivocally induced seismcity and triggered the damaging earthquake. In this talk, I will review the geological and geophysical observations that underpinned the inquiry’s findings, focussing in particular on the sequence of events that occurred during each phase of injections and the lessons this earthquake provides for managing risks associated with induced seismicity.
Biography: John Townend is a Professor of Geophysics and former Head of the School of Geography, Environment and Earth Sciences at Te Herenga Waka—Victoria University of Wellington. He was born and grew up in Rotorua, New Zealand, and educated at University of Otago, Massey University, and Stanford University, where he completed his PhD in geophysics in 2003. Prof Townend’s research focuses primarily on the mechanics of faulting, the detection and seismotectonic characterisation of microseismicity, and fault zone structure and hydrology. In 2017 and 2018, he served on the Overseas Research Advisory Committee of the Geological Society of Korea’s inquiry into the Pohang Earthquake.